HP XP7 Storage - Manual (Page 30)

The maximum number of pairs is determined by the following:
•
The number of bitmap areas required for Continuous Access Journal Z (calculated above).
•
The total number of bitmap areas in the storage system, which is 65,536.
Bitmap areas reside in an additional shared memory, which is required for Continuous Access
Journal Z.
◦ Bitmap areas are used not only by Continuous Access Journal Z, but also by Continuous
Access Journal, Continuous Access Synchronous, and Continuous Access Synchronous
Z. Therefore, the number of bitmap areas used by these other program products (if any)
must be subtracted from 65,536, with the difference used to calculate the maximum
number of pairs for Continuous Access Journal Z.
◦
If Continuous Access Synchronous Z and Continuous Access Journal Z share the same
volume, you must use the total number of bitmap areas for both pairs regardless of whether
the shared volume is primary or secondary.
•
The maximum number of pairs supported per storage system, which is 65,280.
Calculate the maximum number of pairs using the following formula if you use Virtual LVI volumes.
If you do not use them, see
Table 5 (page 30) .
Maximum number of pairs = floor( Number of bitmap areas / required
number of bitmap areas )
If the calculated maximum number of pairs exceeds the total number of LDEVs, then the total number
of LDEVs is the maximum number of pairs that can be created.
The following table lists the maximum number of pairs that can be created according to emulation
type — when Virtual LVI volumes are not used.
Table 5 Maximum number of pairs per emulation type when Virtual LVI volume not used
Maximum number of pairs Emulation type
64K LDEV, BC/VM Extension TPF Additional shared memory
65,280 16,384 3390-1
65,280 16,384 3390-2
65,280 16,384 3390-3
32,768 16,384 3390-9
1.985 1,985 3390-A
13,107 13,107 3390-L
7,281 7,281 3390-M
Maximum initial copy operations and priorities
During configuration, you specify the maximum number of initial copies that can be run at one
time. The system allows up to 2048 initial copies to run concurrently. You do this for performance
reasons (the more initial copies running concurrently, the slower the performance).
You will also specify the priority for each initial copy during the create pair operation. Priority is
used when you are creating multiple initial copies during an operation. Creating multiple initial
copies in one operation is possible because you can specify multiple P-VOLs and S-VOLs in the
Paircreate dialog box. The pair with priority 1 runs first, and so on.
When you create more pairs than the maximum initial copy setting, the pairs with priorities within
the maximum number specified run concurrently, while the pairs with priorities higher than the
maximum number wait. When one pair completes, a waiting pair begins, and so on.
30 Planning volumes, XP7 systems